Fused switch



Feb, 4, 1941. w FRANK 2,230,426

FUSED SWITCH Filed April 5, 1939 F1 g 2 INSULATION Patented Feb. 4, 1941 UNITED STATES PATENT OFFICE Claims.

This application relates to fused switches or thelike.

A fused swltchgenerally comprises a stationary contact adapted to be engaged by a movable contact for switching purposes, with the sta tionary contact permanently electrically connected to a fuse clip or fuse holder into which is adapted to be inserted one end of .a cartridge fuse, there being a second fuse clip, remote from the first, for receiving the other end of the cartrid'ze fuse.

In this application there is disclosed a construction wherein the fuse clip and stationary contact are so disposed relatively, with the path between them so formed, that though they are relatively closely adjacent, high temperatures arising in the clip are preventedfrom reaching the contact, but the electrical conductivity of the conducting path between the clip and the contact is good.

Embodiments of the invention are disclosed in the appended drawing. In this drawing,

Fig. 1 is a cut away plan view of a fused switch containing one form of connection between a clip and a contact;

Fig. 2 is a section on line 22 oi Fig. 1;

Fig. 1 shows a fused switch comprising a sheet metal box It provided with a movable cover ll. Mounted on the back of the box is an insulation base 12 supporting stationary contacts ll adapted to be interconneced and bridged by -the duplex movable contact l5 disposed within an insulation housing I6 movable on and telescoping over the free ends of the stationary contacts. To one of these stationary contacts is connected a binding post H for a line conductor-terminal. To the other is connected a fuse clip 18 for-receiving one end of a cartridge fuse is whose other end is received in a fuse clip 20 connected by a strap 2| to a binding post 22 for a load-conductor terminal.

The fuse clip I 8 is U-shaped. To its bight is secured a copper block 24 connected by a plurality of hair pin wires 25 of copper to a second copper block 26 in turn connected directly to the stationary contact H. The parts 242526 electrically connect the clip and the contact.

It will be observed that the parts 24, 25, 25 which provide the electrical path between the clip and the contact has a great tendency to reduce the flow of heat between clip and contact,

more than that which would be the case if the wires 25 were shaped ina single block of copper to form an electrical path of less electrical resiatance than is provided by the wires in the shape indicated. Thus, the wires may be considered to be so shaped that though their electrical resistance is slightly larger than that of an equivalent weight and quantity of copper formed into a block, representing the minimum 6 electrical resistance from such weight and quantity of copper, the heat flow resistance of that weight and quantity of copper when the copper is formed into radiating wires 25 is considerably greater than would be the case if the copper were formed into a block. Therefore, though the amount of heat generated in the electrical path between the clip and the contact is slightly greater than the minimum that could be obtained from an equivalent quantity of copper, the

heat flow resistance of the path is considerably greater, thus resulting in a net gain of heat flow resistance in the path between the clip and the contact.

To minimize the flow of heat between blocks 24 and 26, there may be an air gap between them and this may be increased as desired. Besides, the air gap may be filled with a heat insulation barrier 21, as indicated, to minimize heat flow between blocks 24 and 26.

, The housing I 6 forms .a wall or shield for the contact set "-45, minimizing heat radiation to it from the clip I8, and thus permits the clip to be brought much closer to the contact set l4-|5, with no increase in heating of the latter 30 than would be the case if there were no shield.

Now having described the fused switch hereof, reference should be had to the claims which follow for a. determination of the invention.

I claim:

1. An enclosed box type fused switch having a contact malnng and breaking set, and a fuse retainer in close physical proximity thereto, means providing an electrically conducting path between the contact set and the fuse retainer and formed for elfectively dissipating heat therein and thus reducing the flow of heat between the contact set and the fuse retainer.

2. An enclosed box type fused switch having a contact making and breaking set, and a fuse retainer in close physical proximity thereto, means providing an electrically conducting path be tween the contact set and the fuse retainer and formed for, effectively dissipating heat therein and thus reducing the flow of heat between the contact set and the fuse retainer, the means being so shaped that though its electrical resistance is no less than or is even slightly greater than the minimum that could be obtained from the equivalent weight and quantity of the mate- (it rial of which the means is formed, its heat flow resistance is considerably greater than the minimum. V

3. An enclosed box type fused switch having a contact making and breaking set, and a fuse retainer in close physical proximity thereto; means providing an electrically conducting path between the contact set and the fuse retainer and formed for efl'ectively dissipating heat therein and thus reducing the flow of heat between the contact set and the fuse retainer, the contact set having a wall of insulation formed around it and providing a heat flow resistant shield between the contact set and the fuse retainer.

4. An enclosed box type fused switch having a contact making and breaking set, and a fuse retainer in close physical proximity thereto, means providing an electrically conducting path l between the contact set and the fuse retainer and formed for eifectively dissipating heat therein and thus reducing the flow of heat between the contact set and the fuse retainer, the contact set )having a wall of insulation formed around it and providing a heat flow resistant shield between the contact set and the fuse retainer, the wall being part of a movable housing of insulation within which is the movable contact and the engaged part of the stationary con tact.

5. An enclosed box type fused switch having a contact making and breaking set, and a fuse retainer in close physical proximity thereto, means providing an electrically conducting path between the contact set and the fuse retainer and formed for effectively dissipating heat therein and thus reducing the flow of heat between the contact set and the fuse retainer, the means being so shaped that though its electrical resistance is no less than or is even slightly greater than the minimum that could be obtained from the equivalent weight and quantity of the material of which the means is formed, its heat flow resistance is considerably greater than the minimum, the contact set having a wall of insulation formed around it and providing a heat flow resistant shield between the contact set and the fuse retainer, the wall being part of a movable housing of insulation within which is the movahis contact and the engaged part of the stationary contact. v

WILLIAM H. FRANK. 

